Experimental behavior and design of a new kinematic isolator

This paper reports on the experimental behavior and design of a rolling self-centering precast prestressed pile (PPP) isolator. This isolation device was developed as an alternative for use in light-weight and low-cost housing located in sites with poor soils. The specimens tested had a spherical and flat–spherical top and bottom end rolling surfaces, respectively, and they generate the self-centering action by a prestressed central cable. Eight full-scale PPP specimens were tested, including two with yielding reinforcement bars at the rolling interface. The axial load on the tested specimens was constant and equal to 147.2 kN, which corresponds to a typical vertical load on a PPP for the types of building considered in this research. The experimental results validate in general the predictions of the analytical model presented; however, the theoretical model is not able to predict the energy dissipation observed in specimens without passive reinforcement, and the apparent larger initial flexibility in the element force–displacement relationship. Additionally, a procedure is developed for simplified isolation design of light-weight structures, which combines the use of flat–spherical PPPs and steel–Teflon sliders in parallel. As an example, the procedure was tested on a design alternative for a low cost housing complex built under conventional fixed-to-base foundations.